Position a rack in the middle of the oven and preheat to 350 degrees. Butter and flour a 5x9-inch loaf pan.

Sift the flour, baking powder and salt into a medium bowl. Combine the sugar, eggs, and vanilla paste in a food processor container and process for 5 seconds.

Melt the butter slowly in a microwave-safe measuring cup or in a saucepan on the stove. Stir the butter to combine the milk solids with the butter fat. Pour the butter through the food processor feed tube in a slow steady stream, processing constantly. Spoon the mixture into a large bowl. Fold in the sifted dry ingredients in three stages until just combined.

Pour the batter into the prepared pan. Bake for 15 minutes. Reduce the temperature to 325 degrees. Bake for an additional 35 to 40 minutes or until golden brown, rotating the pan halfway through the baking time.